Republicans act shocked that their party might as well be one of Donald Trump’s hotels with his name plastered on it. He is almost certain to win the Arizona primary on Tuesday, and barring a miracle or a coup at the convention, he will be the Republican presidential nominee. Many millions have been spent by the anti-Trump forces, to no avail. A prominent mainstream member of the party recently told me that donors met secretly in a restaurant to plot their next move, but the only decision they have made was how they would like their steak done.

No one should be surprised. It takes a big tent to house both Trump -- the non-Golden Rule billionaire with New York values and five children by three wives -- and Billy Graham, but that’s what the Republicans built. The party of Main Street hung out a welcome sign to resentful white southerners, Tea Partyers, home schoolers, anti-tax, anti-spend fiscal conservatives, evangelicals and militiamen; those who embrace creationism and reject science, and anyone with a grudge, not to mention isolationists and hawks. To those who long to deport undocumented immigrants, love automatic weapons and believe global warming is an Al Gore hoax, the party said "come on in."

Trump rushed into the vacuum created by the open-door policy. His brassy showmanship, his garish success, and his big checks to candidates earned him a celebrity perch similar to Clint Eastwood’s before he talked nonsense to an empty chair at the 2008 convention.

It all came in handy as he campaigned in Arizona this week with the endorsement of a fellow Republican politico-celeb, the tough, immigrant-baiting Sheriff Joe Arpaio. Despite an increasing Hispanic population, he’s won six straight elections in Maricopa County, which contains almost two-thirds of Arizona's population. Others pursued Arpaio’s help (including Senator Ted Cruz) even though he is known for rounding up Hispanics and has pending civil contempt charges for defying orders to stop the practice. For fun, he’s forced jail inmates to wear pink underwear and to live outside in tents in searing heat.

Trump's likely victory in Arizona will show that a right-wing populist can use racist undertones to thrive, by enraging and engaging the forgotten white working class without actually helping them. He’s not even in favor of raising the minimum wage.

Arpaio and Trump are exemplars of what Republican National Committee Chairman Reince Priebus warned against in his autopsy of the party's 2012 drubbing. He said that if the party was ever to regain the presidency, it would have to give up anger and tearing down in favor of optimism and building up. It’s too late. Trump and Arpaio rose to prominence as leaders of the angry birther movement committed to tearing down Obama. Trump’s name recognition made him a regular spokesman on television and his money funded investigators aiming to prove that President Barack Obama wasn’t a natural citizen, but a Kenyan-born Muslim socialist. If a Republican, save Senators John McCain and Lindsey Graham, blasted this crazed effort to delegitimize Obama, it went unnoticed. Polls found that while 62 percent of Americans said they believed Obama was born here, 24 percent thought he wasn't and 14 percent were unsure. Of the doubters, 62 percent were Republicans.

And Arpaio and Trump had back-up. Senate Majority Leader Mitch McConnell fed the base by pledging to do everything in his power to make Obama a one-term president. The obstruction continues with his refusal to give Obama's Supreme Court nominee, Judge Merrick Garland, as much as a meeting with Republican senators, citing non-existent precedents.

Trump is not an outlier but what the party should have expected. While the sit-downs in non-smoke-filled rooms continue, the party is cooked. Some Republicans are lining up behind Trump -- Governors Chris Christie and Rick Scott, Ben Carson and the former House speaker, Newt Gingrich. Others dance around it. Speaker Paul Ryan condemns specific Trump outrages -- the stoking of anger and violence, the attacks on Muslims, the lack of seriousness -- but says that he will “respect the primary voter.” Still others are whispering cheerfully that Trump might pull off the hat trick of enraging minorities but winning anyway with an outpouring of angry white males.

The big tent worked out. Trump was let in. Now the Republican Party is another Trump-branded property.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.